Sol-Gel Chemistry of Hydrogenosiliconates: The Role of Hypervalent Silicon Species

1990 ◽  
Vol 180 ◽  
Author(s):  
V. Belot ◽  
R. Corriu ◽  
C. Guerin ◽  
B. Henner ◽  
D. Leclercq ◽  
...  
Keyword(s):  
Sol Gel ◽  
Condensation Reactions ◽  
Sol Gel Process ◽  
Redistribution Reactions ◽  
Hydrolysis Of

ABSTRACTThe hydrolysis of organic silicates ( mainly Si(OEt)4: [TEOS] and Si(OMe)4: [TMOS]) is the key reaction in sol gel process for preparation of silica. The mechanism of this reaction is not well known because of the competition taking place between hydrolysis itself and condensation reactions (homo or heterocondensations) but also because of redistribution reactions which take place competitively. Furthermore the competition between these steps depends also on the catalysis (acid,basic or nucleophilic) [1, 3].

scholarly journals Cyanate Ester Resin/Silica subnanocomposites and their superiority over nanocomposites due to fundamental role of constrained interfacial dynamics

2021 ◽  
Vol 2103 (1) ◽  
pp. 012100
Author(s):  
V A Bershtein ◽  
A M Fainleib ◽  
D A Kirilenko ◽  
P N Yakushev
Keyword(s):  
Positive Impact ◽  
Sol Gel ◽  
Cyanate Ester ◽  
Interfacial Dynamics ◽  
Cyanate Ester Resin ◽  
Sol Gel Process ◽  
Matrix Properties ◽  
Interfacial Areas ◽  
The Matrix

Abstract The study of nanostructure, thermal and relaxation properties (by HAADF-STEM, EDXS, DMA and DSC), combined with the calculations of interparticle distances and interfacial areas, has been performed for a series of the hybrid Cyanate Ester Resin (CER)/Si02 polymer composites with 0.01 to 10 wt.% Si02 units introduced via a sol-gel process. The absence of clusterization, arising only subnanometric Si02 nodes and their quasi-regular distribution within the amorphous matrix, with the shortest distances between nodes, provided their exceptional positive impact on the matrix properties at ultra-low Si02 contents of 0.03-0.1 wt.%. The superiority of these subnanocomposites over the nanocomposites was determined by the role of constrained interfacial dynamics over the whole matrix.

Organic–inorganic hybrids having a talc-like structure as suitable hosts to guest a wide range of species

2018 ◽  
Vol 47 (9) ◽  
pp. 2925-2932 ◽  
Author(s):  
J. Brendlé
Keyword(s):  
Hybrid Materials ◽  
Sol Gel ◽  
Step Method ◽  
Mild Conditions ◽  
Condensation Reactions ◽  
Wide Range ◽  
Sol Gel Process ◽  
Hydrolysis And Condensation ◽  
One Step

The sol–gel process involving hydrolysis and condensation reactions is an attractive way to form siloxane based hybrid materials since it is a one-step method performed under mild conditions.

Synthesis of Hollow Titania Photocatalytic Particles Using Yeast as Templates

2013 ◽  
Vol 699 ◽  
pp. 126-132 ◽  
Author(s):  
Toshiyuki Nomura ◽  
Syota Tanii ◽  
Hayato Tokumoto ◽  
Yasuhiro Konishi
Keyword(s):  
Pore Diameter ◽  
Sol Gel ◽  
Solid Particles ◽  
Core Shell ◽  
Average Pore ◽  
Inorganic Particles ◽  
Sol Gel Process ◽  
Yeast Powder ◽  
Titania Precursor ◽  
Hydrolysis Of

Hollow inorganic particles have attracted considerable interest for a variety of applications. In this work, yeast powder was used as a bio-template to fabricate yeast/titania core-shell spheres. A titania precursor was deposited via the hydrolysis of tetraisopropyl titanate. Triethanolamine was employed to control the reaction rate of the sol-gel process. The hollow titania particles with a diameter of approximately 4 m and a thickness of approximately 54 nm were successfully obtained after calcination of the core-shell spheres at 700 °C. The crystal structure of the particles was anatase. The specific surface area and the average pore diameter were 21.4 m2/g and 1.6 nm, respectively. The photocatalytic activity of the hollow particles was higher compared with that of solid particles.

Homogeneous phase synthesis of chitosan silica hybrid materials in ionic liquid medium and adsorption of Fe(III) from aqueous solutions

2019 ◽  
Vol 38 (9) ◽  
pp. 586-597 ◽  
Author(s):  
Ananda S. Amarasekara ◽  
Deping Wang
Keyword(s):  
Ionic Liquid ◽  
Hybrid Materials ◽  
Sol Gel ◽  
Phase Reaction ◽  
Phase Synthesis ◽  
Homogeneous Phase ◽  
Sol Gel Process ◽  
Hydrolysis Of ◽  
Silica Hybrid ◽  
Ionic Liquid Medium

Two chitosan silica hybrid materials were prepared by a two-step process in 78–84% yields using the homogeneous phase reaction of 3-(triethoxysilyl)propyl isocyanate with chitosan dissolved in 1-n-butyl-3-methylimidazolium chloride ionic liquid (∼10% w/w), which was followed by NH4OH catalyzed hydrolysis of triethoxysilyl groups and then sol-gel process. These new hybrid materials were shown to adsorb up to about 95% of Fe3+ from 5 × 10−4 M aqueous solution at room temperature in 24 h.

Sol-Gel Process form Heterometallic Alkoxides to Incorporate Alkaline- and Rare Earths in Alumina for automotive Applications

1996 ◽  
Vol 431 ◽  
Author(s):  
C. K. Narula
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Automotive Applications ◽  
Automotive Catalysts ◽  
Heterometallic Alkoxides ◽  
Sol Gel Process ◽  
Alkaline Earths ◽  
Cost Of Materials ◽  
Gel Processing

AbstractThe high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, we briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. We will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.

scholarly journals Spinnability of Silica Sols: the Role of Alkoxy Group Exchange

1994 ◽  
Vol 346 ◽  
Author(s):  
S. Prabakar ◽  
R.A. Assink ◽  
A.D. Irwin
Keyword(s):  
Sol Gel ◽  
Alkoxy Group ◽  
Condensation Reactions ◽  
Hydrolysis And Condensation ◽  
Silica Sols

ABSTRACTThe exchange and spinnability of several systems with the general form Si(OR)4 (where R = CH3, C2H5) in ethanol, propanol and butanol were investigated. We have followed the alkoxy group exchange, the hydrolysis and condensation reactions and the Q distributions of these systems using 29Si and 17O NMR. The observed differences in spinnability of the various sol-gel systems are attributed to the effect of the bulkiness of the alkoxy group on its reactivity.

Preparation and Electrophoretic Deposition of an Yttrium Silicate Precursor Sol

2009 ◽  
Vol 412 ◽  
pp. 267-272 ◽  
Author(s):  
Jana Grosse-Brauckmann ◽  
Günter Borchardt ◽  
Christos Argirusis
Keyword(s):  
Electrophoretic Deposition ◽  
Sol Gel ◽  
Constant Current ◽  
Particle Charge ◽  
Yttrium Silicate ◽  
Micro Cracks ◽  
Sol Gel Process ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

. In the present work we used the sol-gel process to prepare Y2SiO5 precursor sols suitable for electrophoretic deposition (EPD). The sol synthesis was performed through the controlled hydrolysis of alkoxide solutions of tetraethoxysilane and yttriumoxoisopropoxide. During sol development emphasis was put on characterization of particles size and zeta potential of the formed aggregates. We succeeded in synthesizing a clear sol containing polymeric aggregates with acceptable particle charge. The electrophoretic deposition on glassy carbon or C/C-SiC slabs led to homogenous layers. At low sol concentrations micro cracks in the deposited layers were observed whereas higher concentrations led to thin and dense layers. During constant current EPD a constant voltage was recorded indicating that the deposited layer does not lead to an increase in resistivity in this kind of EPD system.

Leaching Behavior of Edta In A Silica Sol-Gel Matrix

1994 ◽  
Vol 346 ◽  
Author(s):  
Kris S. Oka ◽  
J.D. Mackenzie
Keyword(s):  
Pore Volume ◽  
Sol Gel ◽  
Silica Matrix ◽  
Silica Gels ◽  
Volume Distribution ◽  
Leaching Behavior ◽  
Sol Gel Process ◽  
The Matrix ◽  
Physical Changes ◽  
Hydrolysis Of

ABSTRACTEthylene diamine tetra-acetic acid (EDTA) doped silica gels were made by the sol-gel process for the potential application as a filter for heavy metal ions in wastewater. The behavior of the organic molecule in the matrix was studied by investigating the percentage of EDTA leached out with a variation in the timing of addition of the EDTA molecule into the starting silica gel solution. Leach tests using water as the medium were performed for 2, 12 and 24 hours in order to determine the amount of EDTA trapped in the pores or in the matrix. A minimum amount of EDTA leached from the gels was detected in the samples to which EDTA was added 4 hours after initial hydrolysis of TEOS. This result was correlated to having a greater percentage of pore volume in the range of 15–20 Å, which was further substantiated with density measurements. The physical changes in the silica matrix altering the pore volume distribution were attributed to the addition of the water into which the EDTA molecule was initially dissolved.

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